Separating metals by electrolysis



N. V. HYBINETTE.

SEPABATING METALS BY HECTROLYSIS.

APPLICATION FILED FEB, 16, I920- Patented Nov. 1, 1921. R

m M w 2M mm; W 8

N0 v'ro'ron HYBINETTE, or CHRISTIANIA, NORWAY.

SEPARATING METALS BY ELECTROLYSIS.

Specification of Letters Patent;

Patented New, 19211.

Application filed February 16, 1920. Serial No. 358,968.

T 0 all whom it may concern:

Be it known thatI, NOAK VICTOR HYBIN- ET'rE, a citizen of Norway,residing at Christiania, Norway, have invented certain new and usefulImprovements in Separating Metals by Electrolysis; and I do herebydeclare the. following to be a full, clear, and exact description of theinvention, such as will enable others skilled in the art to which itappertains to make and use the same.

In Letters Patent of the United States of America No. 805,969, issuedNovember 28, 1905, I'have described and claimed a process for theseparation of metals consisting mainly in smelting ore into more or lesspure copper-nickel anodes, which are then electrolyzed in a cell orcells, having a so-called filter which separates the anode compartmentfrom the cathode v compartment, a stream of neutral nickel sulfatesolution runnin into the cathode compartment continuous y and thencethrough the filter, whereby the copper as it dissolves from the anode isprevented from entering the cathode compartment, and a pure nickel.deposit is produced upon the cathode.

, In this process, the metals dissolved at the anode make the-nickelsulfate solution passing from the cathode compartment into the anodecompartment impure, and it is regens erated'by cementation of copper onnickel,

and, eventually, by precipitating iron bymeans of nickel oxid. Theliquid thus regenerated; and purified is again supplied to theelectrolytic tank. s

It is well known that-a good cathode deposit of nickel is dependent uponthe employment of an absolutely. neutral plating solution, with orwithout the addition of a number of dopes known to the art and V whichare referred to in the patent as weak acids. If, however, free sulfuricacid in the solution should rise to a content of more than a fewhundredths of one per cent., or

if, on the other hand, the solution should become slightly 'basic, thenickel deposit will be immediately injuriously aifected,--in the firstinstance becoming hard and brittle,

V and, in the latter instance, being soft, po-

to keep the solution of the correct acidity rous and mixed with basisprecipitate.

It is, therefore, of the greatest importance Accordingly, in my U. S.patent above referred to, I have specified that the filter Should bevery porous so that it would not assured.

act as a dialytic diaphragm, that is to say, that 1t would not causedialysis of the oathode solution by the migration of any notable amountof acid ions through the filter;

in other words, the provisions made inmy patent were such that theacidity of the solutlon would be very slight on both'sides of thefilter. a i

I have found, however, that the use of filters of the very porous typecontemplated by the patentinvolv'es the circulation of a large quantityof solution and that, accordingly, the operation of the process iscorrespondingly more xpensive than if a smaller quantity of solutioncould be circulated. I have also found that, in certain instances, it isnecessaryto maintaina greater degree of acidity of the solution on theanode side than on the cathode side of the filter. Thus, the anodeefliciency of the current, in neutral solution, is considerably lessthan the cathode efficlenc in those instances where use is made 0 a lesseasily soluble anode, such as hereinafterdescribed to increase the anodeefliciency, under such conditions, it is desirable to have a greateracidity in the anode compartment than that permissible for good platingon the cathode.

The present invention is intended to correct the defects hereinbeforenoted. In carrying the invention into effect. instead of supplying tothe cathode compartment a neutral solution (with or without the additionof the dopes or weak acids. sometimes employed) I make use of a nickelsulfate solution, continually flowing into the cathode compartment, andcontaining a notable proportion of free sulfuric acid. In fact, in thepreferred practice of the invention the solu-.

tion as it enters thecathode compartment, is so acid that commerciallygood nickel can- 'not normally be plated from it; nevertheless, 111accordance with the present invention, such commercial plating isabsolutely The way in which 7 parent paradox is by using a densediaphragm instead of the orous filter partition of the patent, therey-correspondingly cutting down the amount of solution circulated perunit of time, while, at the same time, the dense diaphragm acts notmerely as a filter-to direct the circulation, as setforth. in thepatent, but part] as a diaphragm and. partlyas a filter. Y 'urthermore,

I accomplish this apthe speed of filtration flow through the diaphragm,the acidity and the nickel content of the ingoing electrolytic';solution, the dialytic capacity of the diaphragm, the temperature ofthe electrolyte, and finally, the current density.

For instance, for good plating, I use a solution of nickel sulfatecontaining about 50 grams of metallic nickel per liter continuallyflowing into the cathode compartment with a temperature of about 55 C.and with an acidity of about two grams of free sulfuric acid per liter.A sample of the solution, taken near the cathode, during the platingoperation, will then show about 0.2 grams of free sulfuric acid perliter, an amount small enough to be suitable for good commercialplating. These results are obtained when using a diaphragm of heavycotton cloth which lets through only about one liter per square foot ofsurface per hour, with a hydrostatic pressure in the cathode compartmentranging from about one-half inch to one inch, while the density of thecurrent is about ten amperes per square foot. Under these circumstances,the migration of the acid ions is so much more rapid than the filtrationflow that technically valuable results are obtainable, as

noted. It also appears that the speed of migration of the acid ions inone direction is enormously greater than that of the copper ions in theother direction, and that this difference in migration, together withthe flow of the electrolyte through the filter, results in exclusion ofthe copper ions. from the cathode-solution. The diaphragm alone will notexclude the copper ions from migrating to the cathode compartment, butthe combined flow through thediaphragm filter and the removal of theelectrolyte from the anode compartment, together with proper regulationof the process, enables contamination of the cathode solution withcopper to be avoided.

t will be understood that the specific conditions mentioned above arecapable of some variation, although these conditions are the ones that Ihave found most advantageous. For example, if a diaphragm is used whichpermits the solution to filter through faster, the acidity Should be 1%-it becomes necessary to see to it that the acid solution from the anodeside is purified so that the acidity remains substantially the samebefore and after such purification.

Copper may be removed from the anode solution without disturbing theacidity. If, however, the anodes contain iron in such amount that it isnecessary to precipitate iron out of the solution by nickel oxid(hydrated or carbonated, as the case may be) so that the solutionbecomes neutralized, it will then be necessary to acidify the solutionafter separating out the iron precipitate. So also, such.acidifi'gcation will be necessary in case the removal of the copper iseffected by agents which neutralize the acidity.

If, therefore, for any reason, the solution has been neutralized, I findit most convenient to restore the acidity by plating out nickel from thesolution, in an electrolytic tank, using insoluble anodes; because, ifthe acidity were to be produced by merely adding acid the equilibrium ofingoing and outgoing acid and nickel in the constantly circulatingelectrolyte would be disturbed. Inasmuch as the solution going out ofthe acid ifying electrolytic tank is to contain more acid than isrequired for good nickel plating, I locate the cathode of the acidifyingelectrolytic tank within a cathode compartment provided with porousdiaphragm walls and obtain the desired plating upon said cathode bycirculating my ordinary pure cathode solution through said diaphragmwalls, exactly as in the main plating tanks, and at the same time thatthe main supply of said pure solution to be acidified passes through theacidifying electrolytic tank on the anode side thereof only.

In the use of the present invention, the amount of electrolyte incirculation is so small as compared with the older practice that it hasbeen found important to provide for a more perfect circulation in thesoluble' I anode cell, and I have, therefore, found it desirable to drawoff the solution, in part at least, at the bottom of the cell. In sodoing, I find that the foul or impure electrolyte per-nickel matte maybe roasted and leached to remove the greater portion'of its copper,

and'the roasted and leached matte, containing from 3 to 4 parts ofnickel to 1 of copper, then mixed with about 10%. of powdered coke andsubjected to an electric furnace op eration with a suitable flux whichpromotes the removal of iron therefrom in the form of a slag; The ironcontent of the nickelcopper alloy can thus be reduced to a smallfraction of 1%,whilethe'alloy can likewise .be freed from the greaterportion of its sul- So also the fur and from occluded gases. alloy canbe heated aboveits melting point tosuch a temperature that it is thinlyfluid.

The alloy is therefore of a different and improved composition ascompared with an alloy produce in a blast furnace; and the anodes castfrom such alloy are likewise distinguished from anodes cast from alloysproduced in a blast'furnace, in that they are dense and hard andrelatively more insoluble, and relatively free from the impurities whichare present in anodes made from blast furnace alloys. vThe use of theimproved anodes, in the process of the present invention, resultsin animproved operation ofthe process. Accordingly, while the process iscapable of operation with anodes made from blast furnace alloys it ismore advantageousv when practised with the improved anodes 7 madeof'electric furnace alloy, and I wish,

therefore, to be understood as claiming the use of these improved anodesin this connection, as well as the process when such anodes are notemployed.

a In the drawing hereunto attached, I have indicated, more or lessdiagrammatically,

the apparatus employed in the carrying out of the process.

Referring to the drawing, A indicates the anode compartment of the maincell coni ingpreferably two grams of free sulfuric.

acld to the liter may be conveniently contained in'a storage receptacle0 at a temperature of about 55 C. and dischargesconsame cementation tankD wherein the coptinuously, during the operation of the process, throughthe valve-controlled inlet pipe f.

One of the outlets for the foul or impure solution from the anodecompartment A is by means of the overflow pipe g, and the other out-lettherefrom is the si hon or like discharge [2. leading from near t ebottom of said anode compartment. These two outlets may convenientlydischarge into the per is deposited out on nickeL From the cementationtank the solution passes to the tank E wherein any iron present isprecipitated by nickel oxid, or the like, thereby neutralizing thesolution. The neutralized solution then passes into the acidifyingelectrolytic tank, whose cathode compartment Gr is of the sameconstruction as the like cathode compartment B of the main cell. Theacidifying electrolytic tank is provided with insoluble anodes z, and asuitable cathode j for the precipitationof nickel is provided in thecathode compartment. The. pure nickel acidified solution for the cathodecell G is supplied continuously from the stora e reservoir C through thevalved pipe m. i suitable pump H located in a return conduit n from theacidifying electrolytic tank F conveys the circulating solution back tothe storage receptacle C. I

From the foregoing description of the mode of operation of theinvention, it will be understood that its main characteristic or basicprinciple consists in introducinginto the cathode compartment of thedepositing cell a solution containing an excess of free acid over theamount that would be tolerated for good commercial plating, and bringiabout such a migration of acid ions throng the diaphragm partition as tointroduce and maintain proper plating conditions. Insofar as I am aware,this characteristic feature is broadly new in the art-of electrolyticseparation of metals. Accordingly, Iwish to be understood as intending,in the appended claims, to protect its use in the platlng, v separatingor refining of not only nickel, but also such metals as ferro-nickel,cobalt, zinc, and the like. So also, it will be apparent that theinvention may be applied not only to operations wherein the anode is asoluble alloy, but also to other combinations; as, for instance, in theproduction of nickel by continuously dissolving nickel carbonate in theelectrolyte and employing in connection. therewith, an insoluble anode,and returning L an only partly neutralized electrolyte to the; cathodecompartment.

I claim:

1. The process of plating metals upon a 125 cathode which is separatedfromwthev anode by a filtering dia hragm, which comprises effecting aflow mm the cathode to the anode of an electrolyte which enters thecathode compartment with an excess of free 0 effecting a cathodecompartment with an excess of free other metals by electrolysis of ananode consulfuric acid beyond the amount to be tolerated at thedepositing surfaces of the oathode, and obtaining the desired conditionof the electrolyte at said surfaces by the migration of acid ionsthrough the diaphragm;

substantially as described.

3. The process of plating metals upon a cathode which is separated fromthe anode by a filtering diaphragm, which comprises efiecting a fiowfrom the cathode to the anode of an electrolyte which enters the cathodecompartment with an excess of free sulfuric acid beyond the amount to betolerated at the depositing surfacesof the oathode, and obtaining anearly neutral conditionof the electrolyte at the depositing surfaces ofthe cathode suitable for commercial metal deposits thereon by themigration of acid ions through said diaphragm; substantially asdescribed.

4. The process of separating nickel from taining an alloy of nickel, andplating nickel at the cathode, which comprises separating the cathodefrom the anode by a filtering diaphragm and effecting a flow from thecathode to the anode of an electrolyte which, at its entrance into thecathode compart- -ment, contains more free sulfuric acid than isappropriate for producing a deposit of.

nickel of commercial quality upon the oath? ode; substantially asdescribed.

5. The process of separating nickel from other metals by electrolysis ofan anode containing an alloy of nickel, and plating nickel at thecathode, which comprises separating the cathode from the anode by afiltering diaphragm and efiecting a How from the cathode to the anode ofan electrolyte which, at its entrance into the cathode compartment,contains more free sulfuric acid than is appropriate for producing adeposit of nickel of commercial quality upon the cathode, regeneratingthe anode solution and acidifying the regenerated solution by causing itto flow through an electrolytic tank with insoluble anodes, in whichtank the desired amount of acid to' regenerate it is set free, and acorresponding amount of nickel is plated; substantially as described.

6. The process of separating nickel from other metals by electrolysis ofan anode containing an alloy of nickel, and plating nickel at thecathode, which comprises separating the cathode from the anode by afiltering dlaphragm and eflecting a flow from. the

cathode to the anode of an electrolyte which, at its entrance into thecathode compartment, contains more free sulfuric acid than isappropriate for producing a deposit of nickel of commercial quality uponthe cathode, re generating the anode solution and acidifying theregenerated solution by causing it to flow through the anode compartmentonly of an electrolytic tank having insoluble anodes and equipped withfiltering diaphragms around its cathodes and maintaining a flow ofplating electrolyte from the cathode compartment into the anodecompartment of said acidifying electrolytic tank; substantiallyas'described.

7 In the electrolysis of metals, regenerating an acid anode electrolytecontaining in solution nickel and another metal by depositing out theother metal by a precipitant which neutralizes the solution, andthereupon restoring the electrolyte to its original condition of acidityby plating out a portion of the nickel therefrom; substantially asdescribed.

8. The rocess of plating nickel upon a cathode w ich is separated fromthe anode by a filtering diaphragm, which comprises supplying to thecathode compartment at a temperature of about 55 C. a nickel sulfateelectrolyte containing about 50 grams of nickel per liter and having anacidity of about 2 grams of free sulfuric acid per liter, and effectinga flow of the electrolyte from the cathode compartment to the anodecompartment through the filtering diaphragm, the current density, therate of flow, and the diaphragm being such that the acidity of theelectrolyte near the cathode will be reduced to about 0.2 grams of freesulfuric acid per liter substantially as described.

about 2 grams of free sulfuric acid per liter,

effecting a flow of the electrolyte from the cathode compartment tothe'anode compartment through the filtering diaphragm at the rate ofabout 1 liter per square foot of surface per hour, and maintaining acurrent density of about 10 amperes per square foot, the nature of thediaphragm and the regulation of the process being such that the acidityof the electrolyte near the cathode will be reduced toabout'f02 grams offree sulfuric acid per liter; substantially as described; v

10. The process of plating nickel upon a cathode which is separated froma co per nickel anode by a filtering diaphragm, w lch comprisesefl'ecting aflow from the anode to 190 the cathode of a nickel sulfateelectrolyte which enters the cathode compartment wlth an excess of freesulfuric acid beyond the amountto be tolerated at the depositingsurfaces of the cathode, and drawing off a part at least of the impureelectrolyte from the bottom of the anode compartment; substantially asdescribed. a

11'. The process of plating nickel upon a cathode which is separatedfrom a copper nickel anode by a filtering diaphragm, WhlCh compriseseifecting a flow from the anode to the cathode of a nickel sulfateelectrolyte I which enters the cathode compartment with stantially asdescribed an excess of free sulfuric acid beyond the amount to betolerated at the depositing surfaces of the cathode, and drawing off apart of the impure anode electrolyte from the top of the anodecompartment and a part from the bottom of the anode compartment; sub-12. The process of plating nickel upon a cathode which is separated froma, nickel nace; substantially as described.

13. Electrolytic apparatus, comprising an anode compartment and acathode compartment, provided respectively with anode and "cathode, andseparated from each other by a filtering diaphragm, and means forsupplying a fiow of the electrolyte to the oath ode compartment and fromthe anode compartment,

said filtering diaphragm being of such permeability that it'acts partlyas a filter andpartly :as a diaphragm to deplete the solution-in thecathode compartment in acid ions substantially as described.

14. Electrolytic apparatus, comprising an anode compartment and acathode compartment, provided respectively with a'copper nickel anodeand a cathode forthe deposit of nickel thereon, and separated from eachother by a filtering diaphragm, means for supplying to the cathodecompartment a flow of nickel sulfate electrolyte and for removing fromthe anode compartment the copper-nickel electrolyte, said filteringdiaphragm being of such permeability that it acts partly as a filter andpartly as a diaphragm to deplete the solution in the cathode compartmentin acid ions; substantially as described. Q

15 Electrolyticiapparatus, comprising an anodecompartment and a cathodecompartment, provided respectively with a coppernickel anode and acathode for the deposit of nickel thereon, and separated from each otherby a filtering diaphragm, means for supplying a flow of nickel sulfateelectrolyte containing an excess of acid to the oathode compartment,means for drawing 0E a part at least of the impure nickel-copperelectrolyte from the anode compartment, said filtering diaphragm beingof such permeability that it acts partly as a filter and partly as adiaphragm to deplete the solu tion in the cathode compartment in acidions; substantially as described.

In testimony whereof I afiix my signature.

'NoAK vrcron rrrnrnnrrn.

